SSP seminar

Evidence for a Turnover in the Low Mass IMF: Analysis from an Ensemble of Young Clusters

Michael R. Meyer (Steward Observatory, University of Arizona)

Monday 14th July 2008, 12:00pm
Pratt conference room, 60 Garden Street

Astronomers have known for almost a decade that sub-stellar objects do not contribute significantly to the dynamical mass of normal stellar populations (e.g. Reid et al. 1999). Yet until recently there remained considerable debate whether brown dwarfs might outnumber stars (e.g. Allen et al. 2005). We set out to explore, in a quantitative way, whether we could rule out the hypothesis that the slope of the initial mass function continued to rise into the brown dwarf regime using an ensemble of results from seven deep surveys of various young star clusters. We first demonstrate that the ratios of stars to brown dwarfs are consistent with a single underlying IMF. With this assumption, we then combine the ratios of stars to brown dwarfs from each cluster in order to constrain the shape of the low mass IMF, finding it to be consistent with the log-normal form of Chabrier (2005). This analysis indicates, with high confidence (P > 99.99%), that the sub-stellar IMF turns over (dN/dM M^(-alpha), alpha < 0). More information can be found at


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